(1) Field of the Invention
The present invention relates generally to forms for poured concrete roof and floor decks, and more particularly to an improved form system for on-site concrete structural joists that may be integrated into the concrete deck formed by the forms or otherwise used as structural supports.
(2) Background Information
It is well known in the construction industry to utilize expanded plastic material for forms used in the construction of poured concrete walls, joists and the like. In the formation of walls or joists, the expanded plastic forms may either be removed once the concrete has hardened, or left in place to provide thermal and sound insulation to the completed structure. U.S. Pat. No. 6,817,150 to Boeshart, which is incorporated herein by reference in its entirety, is one example of such a system.
In the field of construction of concrete structural joists there exists a desire to make such joists as strong as possible while at the same time keeping the cost of making such joists as low as possible.